The invention relates to gas turbines, in particular for airplane engines or industrial turbines. The invention relates more particularly to leaktight mounting of a high pressure (HP) turbine nozzle to the downstream end of a combustion chamber.
In a gas turbine having an annular combustion chamber, proposals have already been made to mount the high pressure turbine nozzle by connecting it mechanically to a downstream end portion of the combustion chamber (throughout this application, the terms “upstream” and “downstream” are used relative to the flow direction of the combustion gas produced in the chamber). The assembly formed by the combustion chamber and the HP turbine nozzle can then be supported by connection ferrules connected to inner and outer metal shrouds.
Such a disposition serves to provide better continuity for the gas stream at the interface between the combustion chamber and the turbine nozzle, thus making it easier to provide sealing at said interface, in comparison with a disposition in which the combustion chamber and the HP turbine nozzle are separately connected to the inner and outer metal shrouds.
A combustion chamber with a turbine nozzle integrated in its downstream end portion is shown in document FR 2 825 787. The combustion chamber is made of ceramic matrix composite (CMC) material and the assembly comprising the combustion chamber and the HP turbine nozzle is held between the inner and outer metal shrouds by means of flexible metal connection ferrules that are in the form of sectors so as to make it possible to accommodate the differences between the coefficients of thermal expansion of the metal and of the ceramic composite material.
The turbine nozzle comprises a plurality of stationary vanes secured to internal and external platforms in the form of juxtaposed ring sectors having inside faces defining a flow path through the turbine nozzle for a gas stream coming from the combustion chamber. The mechanical connection between the nozzle and the combustion chamber is provided by means of nuts and threaded rods that are secured to the platforms of the nozzle vanes and that engage in notches formed in the downstream end portions of the inner and outer walls of the combustion chamber.
Sealing can thus be provided at the interface between the combustion chamber and the turbine nozzle. Nevertheless, it remains necessary to seal the stream in the turbine nozzle at the interfaces between the vane platforms.